1. Field of the Invention
The present invention relates to a rotary shaft of a transmission.
2. Description of the Prior Art
In a typical conventional rotary shaft having at a portion of its shaft body a bearing surface and an oil seal surface formed close to each other, the bearing surface and the oil seal surface are often formed on one and the same surface, having a mutual finished surface. In consequence, if the mutual surface is superfinished so as to be suitable for the bearing surface, an oil film may break at the contact area between the superfinished surface and an oil seal and consequently, deterioration due to heat at the oil seal lip part may cause oil leakage. On the other hand, if the mutual surface is abrasive-finished so as to be suitable for the oil seal surface, there may be deterioration in the contact conditions between the abrasive-finished surface and bearing rollers, resulting in an unsatisfactory rotational performance of the rollers. Moreover, if one and the same surface is separately finished so as to be suitable for both the surfaces, such a problem may arise that the boundary between the bearing surface and the oil seal surface has a mottled finished portion.